Air-compressor piston



Dec. 1924b 1,520,853

F. T. CABLE AIR COMPRESSOR PISTON Original Filed June 30, 1920 2 Sheets-Sheet 1 76 eng/ne Zawpressure coo/er INVENTOR mil 7- 1&1. ATTORNEYS 'Dec. 30, 1924.

F. 'r. CABLE AIR COMPRESSOR PISTON original Filed Juh so, 1

2 Sheets-Sheet 2 IINVEN OR W J M A14 ATTORNEYS Patented Dec. 30, 1924.

FRANK '1. CABLE, OF NEW LONDON, CONNECTICUT, ASSIGNOR T0 ELECTRIC BOAT COMPANY, A. CORPORATION OF NEW JERSEY.

AIR-COMPRESSOR PISTON.

Original application filed June 30, 1920, Serial No. 393,066. Divided and this application filed. February 10, 1923. Serial No. 618,257.

To all whom it may concern:

Be it known that I, FRANK T. CABLE, a citizen of the United States, residing at New London, in the county of New London, State of Connecticut, have invented certain new and useful Improvements in Air-Compressor Pistons; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will. enable others skilled in the art to which it appertains to make and use the same.

This invention relates to two-stage air compressors, and more particularly to the second-stage pistons used in such compressors.

According to the present practice the first and second stage pistons of two-stage air compressors are rigidly connected. This makes it necessary that the walls of the first and second stage cylinders be exactly parallel and that the two pistons be in perfect alignment. In practice these conditions are difiicult tomeet, requiring as they do, exact and painstaking workmanship, and as a very slight deviation from exact parallelism between the parts results in rapid wear, particularly in the second stage cylinder, it has been found ditlicult to maintain a tight fit between the secondstagepiston and its cylinder for more than short periods. The wear is taken up in large measure by the snap rings of the piston which must, in consequence, be renewed, some times as often as every two or three months. This operation is difiicult and costly as the compressor must be entirely dismantled and both pistons removed in order to gain access to the second-stage piston.

It is, therefore, clear that could some means be devised for minimizing this wear and obviating the necessity for such frequent. replacements of the second-stage piston rings, a very substantial saving in time and expense could be effected. It is broadly an object of the invention to accomplish this.

Going back to first causes, the origin of the trouble is found in the practical. difii culty of getting perfect alignment between the two cylinders, which are preferably integrally cast and must be machined with most exacting care. This difliculty has been overcome by the present invention through the simple expedient of doing away clearly understood reference is had to the accompanying drawings disclosing One specific embodiment thereof.

In these drawings, Fig. 1 is a section through a two-stage air-compressor equipped with relatively movable pistons designed in accordance with the present invention; and Fig. 2 is a section through the two pistons on an enlarged scale.

In the drawings, 1 represents a two-stage air-compressor. In this compressor, 2 represents the first-stage cylinder, 3 the secondstage cylinder, 4 the first-stage piston, and 5 the second-stage piston, this last being provided with peripheral grooves 6 which fill with oil and serve as seal rings. The walls of the two cylinders are integral cast and form in effect one cylinder having two different bores. The two pistons are connected by means of a bolt 7 which passes through the upper end of the piston 4-, being keyed thereto at 8, and is provided at its upper end with a special nut 9 which bears upon an internal annular flange 10 situated near the upper end of piston 5. This nut is screwed upon threaded end 11 of bolt 7 and locked in position by means of tapered pin 12 which is screwed in the upper end of nut 9'and seated in a tapered and split socket 13 in the threaded end 11 of the bolt. Insertion of pin 12 into socket 18 expands threaded end 11 and fixes the nut 9 tightly in position. Piston 5 is provided at its upper end with a semi-sphen ical cap 14 locked in position by means of screw 15. Cylinder 3 is hushed by means of a removable sleeve or bushing 16 forming the wearing surface for the piston 5.

Play between the two pistons is permitted by clearance spaces 17, 18 and 19. In a case where alignment of the two cylinders hap pened to be particularly bad, piston 5 might I No. 393,066, filed June 30, 1920'.

I claim:

1. In twostage air-compressor the combination of a first-stage piston, a rod extending from the outer end thereof, a nut on the outer end of the rod, a hollow second-stage piston, and an annular flange therein, the nut on the rod bearing against the annular flange to hold the second-stage piston in place on the first-stage piston, there being clearances between the rod and the second-stage piston permitting slight relative movement between the two pistons.

2. In a two-stage air compressor, the combination of a first-stage piston, a. rod extending from the upper end thereof, a nut on the outer end of the rod, a. hollow second-stage piston, and an annular flange therein, dished around its upper and inner periphery, the nut on the rod bearing against the dished portion of the annular flange to hold the second-stage piston in place on the first-stage piston, there being. clearances between the rod and the secondstage piston permitting slight relative move ment between the two pistons.

3. In a two-stage air-compressor, the coml'ajination of a first-stage piston, a rod extending from the outer end thereof, a nut on the outer end of the rod, a hollow secondstage piston, an annular flange'therein, the nut on the rod bearing against the annular flange to hold the second-stage piston in place on the first-stage piston, there being clearances between the rod and the secondstage piston permitting slight relative movement between the two pistons, and a cap on the second-stage piston covering the nut.

4. In a two-stage air-compressor, the combination of a one-piece casting forming the walls of the first and second-stage cylinders in substantial alignment, first and secondstage pistons mounted to reciprocate within their respective cylinders, and means con necting the two pistons permitting slight unrestrained combined relative lateral and angular movement between them to compensate for inaccuracies in the alignment.

'5. In a two-stage air-compressor, the combination of a one-piece casting forming the walls of the first and second-stage cylinders in substantial alignment, first and secondstage pistons mounted to reciprocate within their respective cylinders, said pistons abutting against one another and being provided with a connecting rod loosely connected at each end to one of the pistons so as to permit slight unrestrained 'elative movement between them to compensate for inaccuracies in the alignment of the pistons.

6. In a two-stage air compressor the combination of a first-stage piston, a rod er;- tending from the outer end thereof, a hollow second-stage piston having annular flange therein, means on the rod bearing against the annular flange to hold the second-stage piston in place on the first-stage piston, there being a clearance between the rod and the flange permitting slight relative movement between the two pistons.

7. In a two-stage air-compressor the com-- bination of a first-stage piston, a rod extending from the outer end thereof, a nut on the outer end of the rod, a hollow secondstage piston, and an annular flange therein, the nut on the rod bearing against the annular flange to hold the second-stage piston in place on the first-stage piston, there being a clearance between the inner end of the rod and the second-stage piston permitting slight relative movement between the two pistons.

In testimony whereof I aliiX my signature.

FRANK T. CABLE. 

